16 Dec 2015

The final project reports and sites are now posted: Project Reports

7 Dec 2015

The Evolution of Bitcoin Script Interpreter (Acacia Dai)
A Bandwidth Based “Proof of Work” (Alishan Hassan)
Bitcoin at Point of Sale (Elizabeth Kukla)
西风vpn好用下载 (Collin Berman)
Donation Accountability (Kienan Adams)
Understanding Mobile Bitcoin Wallet (Ziqi Liu)
BitSniffer: a Tool for Linkability Analysis (Ryan Anderson, Sam Prestwood, Luke Gessler)
西风vpn好用下载 (Gardner Fiveash)
How Much is Bitcoin Worth: Pricing Differences Across Exchanges and Time (Quentin Moore)
Analysis of the viability of Bitcoin replacing as a National Currency (Peter Leng)
Evaluating BlockCypher’s Confidence Level (Dean Makovsky and Joseph Tobin and Kevin Zhao and Vignesh Kuppusamy)

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Developing a Distributed Distributed Consensus Protocol Consensus Protocol (Alec Grieser)
Blockchain Voting (Sugat Poudel, Austin J. Varshneya, Xhama Vyas)
西风vpn好用下载 (Carter Hall, Reid Bixler)
Beyond the Lightning Network - Exploring How to Scale Bitcoin (Muthu Chidambaram)
Mixing with Miners (Morgan Locks)
Pruning Nodes (Cyrus Malekpour)
Bitcoin Block-size Options (Michael Parisi Presicce)
新民网 - 为民分忧 与民同乐:2 天前 · 新民网是新民晚报官方网站，强势新闻门户，众上海突发、财经、原创新闻为特色，采用文字、视频、播客、图片、直播等全媒体技术创新报道，另有当日新民晚报数字报纸和新民周刊数字杂志供应。 (Jacob Freck)
Detecting Selfish Mining in Bitcoin and Litecoin (Fangyang Cui)
Geopolitical Strategy and Bitcoin (Eashan Kaw)

30 Nov 2015

Schedule

Wednesday, 2 Dec and Monday 7 Dec: Final Project Presentations. See Class 25 for schedule.

These people are scheduled to present Wednesday: Alec Grieser, (Sugat Poudel, Austin J. Varshneya, Xhama Vyas), (Carter Hall, Reid Bixler), Muthu Chidambaram, Morgan Locks, Cyrus Malekpour, Michael Parisi Presicce, Jacob Freck, Fangyang Cui, Eashan Kaw, Cody Robertson.

Don’t forget to send the link to your presentation before 西风vpn好用下载 on the day you are presenting!

Office hours: normal office hours will continue until December 11: Mondays 5-6:30pm (Ori in Rice 442), Wednesdays after class (Samee in Rice 442), Thursdays 2:30-3:30 (Dave in Rice 507).

Friday, 4 December, 西风vpn好用下载 in Rice 130: Department of Computer Science, Distinguished Alumni Seminar Series

Monday, 7 December (11:59pm): Project Final Reports. See Class 25 for details.

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The slides below include all the Jeopardy questions, even ones we didn’t get to in class. You shouldn’t expect to get asked trivia questions in the oral final exam (and will not be asked to phrase your answers in the form of a question!), but some of the substantive questions here would make good questions to ask during the exam (in particular, I’d recommend looking at the unused questions in Unlocking Script and Crypto Curves as good potential exam questions).

23 Nov 2015

Schedule

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Understanding Mobile Bitcoin Wallet
Ziqi Liu

Visual Explorer for Addresses and their Relations
Ryan Anderson, Sam Prestwood, Luke Gessler

How Much is Bitcoin Worth: Pricing Differences Across Exchanges and Time
Quentin Moore

Analysis of the viability of Bitcoin replacing as a National Currency
Peter Leng

Beyond the Lightning Network - Exploring How to Scale Bitcoin
Muthu Chidambaram

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Morgan Locks

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Michael Parisi Presicce

Bitcoin Controversy and Conflicts of Interest
Jacob Freck

Understanding Takedowns
Gardner Fiveash

网站系统维护中，敬请期待！:2021-6-15 · 系统维护公告 尊敬的厦门网网友： 2021年5月20日21时至6月25日12时，海峡社区、海峡博客平台进行系统维护升级，系统将暂停访问，由此给您带来的不便敬请谅解。
Fangyang Cui

Geopolitical Strategy and Bitcoin
Eashan Kaw

Evaluating BlockCypher’s Confidence Level
Dean Makovsky and Joseph Tobin and Kevin Zhao and Vignesh Kuppusamy

Pruning Nodes
Cyrus Malekpour

Divergence of Alt Coins and their Concurrent Developments
Cody Robertson

A Bandwidth Based “Proof of Work”
Alishan Hassan

Developing a Distributed Distributed Consensus Protocol Consensus Protocol
Alec Grieser

The Evolution of Bitcoin Script Interpreter
Acacia Dai

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The final project presentations will be in class on Wednesday, 2 December and Monday, 7 December. The presentation will count for approximately 50% of the grade for your final project.

The schedule of the presentations is below. Each team will have 5 + (N - 1) minutes to present your project (where N is the number of team members; so a 4-person team will have 8 minutes). Your presentation should be well prepared and enthusiastically delivered!

You should send a link to your presentation (PDF, PowerPoint, or anything that works in Firefox browser) to ccc-staff before 11:59am on the day you are scheduled to present. If your presentation includes a demo that’s great, but it needs to be designed in a way that can be set up quickly and used effectively.

Wednesday, 2 December:
Developing a Distributed Distributed Consensus Protocol Consensus Protocol (Alec Grieser)
Blockchain Voting (Sugat Poudel, Austin J. Varshneya, Xhama Vyas)
Distributed Bitcoin Mixing with Interest (Carter Hall, Reid Bixler)
Beyond the Lightning Network - Exploring How to Scale Bitcoin (Muthu Chidambaram)
Mixing with Miners (Morgan Locks)
Pruning Nodes (Cyrus Malekpour)
Bitcoin Block-size Options (Michael Parisi Presicce)
Bitcoin Controversy and Conflicts of Interest (Jacob Freck)
Detecting Selfish Mining in Bitcoin and Litecoin (Fangyang Cui)
Geopolitical Strategy and Bitcoin (Eashan Kaw)
Divergence of Alt Coins and their Concurrent Developments (Cody Robertson)

Monday, 7 December:
The Evolution of Bitcoin Script Interpreter (Acacia Dai)
A Bandwidth Based “Proof of Work” (Alishan Hassan)
Bitcoin at Point of Sale (Elizabeth Kukla)
Vending on Dark Net Markets (Collin Berman)
Analyzing the Feasibility of a Donation Accountability System in Bitcoin (Kienan Adams)
Understanding Mobile Bitcoin Wallet (Ziqi Liu)
Visual Explorer for Addresses and their Relations (Ryan Anderson, Sam Prestwood, Luke Gessler)
Understanding Takedowns (Gardner Fiveash)
How Much is Bitcoin Worth: Pricing Differences Across Exchanges and Time (Quentin Moore)
Analysis of the viability of Bitcoin replacing as a National Currency (Peter Leng)
Evaluating BlockCypher’s Confidence Level (Dean Makovsky and Joseph Tobin and Kevin Zhao and Vignesh Kuppusamy)

Project Final Reports

To submit your final report, send an email to ccc-staff@cs.virginia.edu with subject line Project Report: Title and cc-ing all of your team members. The official deadline for the final reports is Monday, 7 December (11:59pm), but extensions will be granted upon request so long as extending the deadline for this does not interfere problematically with your other courses and responsibilities.

The email should be plaintext containing:

1. A title for your project (this is the title I will use on the public page listing all the projects; add a * if it is different from the title currently listed on 西风vpn好用下载).

2. A one-sentence description of your project. This should be a clear, well-written sentence that will be enough for someone to understand what you did and why.

3. A URL that points to a publicly-viewable web page that describes your project. The linked page can (and probably should) contain links to other pages (e.g., a website that is your actual project or a github repo with your project code). For example, the link you send could be a link to http://my-project-site.org/about.html or http://github.com/your-repo/README.md, which is a page describing your project, as well as containing links to the main project site. Please try to put your project site somewhere that will not expire when you graduate from UVa, but that can survive forever.

4. Your project report, either as a PDF attachment, or a URL. Your project report should be a well-written and readable paper about your project. For most projects, this should include at least: (1) the motivation for your project, (2) background, including a description of related work (with references), (3) explanation of what you did, and (4) your results. For projects that do not involve building something, it may make more sense for it to be a more integrated report.

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By the end of this week, everyone should receive an email with your status in the class (including feedback on PS3).

The main message of this email will be guidance as to whether or not you should schedule a final exam. The main options are:

1. You’re well positioned to get an A in the class. So long as you do a decent job on the project, you’ll get an A and don’t need to do the final exam.

2. You are approaching what you need to do to convince us you deserve an A in the class, but need do more. If your project is outstanding, that may be enough to make the case. If not, you’ll have a last chance to do so by doing a final exam.

3. From what you’ve done so far, we’re not convinced you understand cryptocurrencies well enough to earn an A in the class. You should plan on doing a final exam to convince us otherwise!

For students receving options 1 or 2, we’ll try to give feedback on your final projects are quickly as possible so you know whether or not a final exam will be recommended.

The final exam will be an oral exam where you will explain how bitcoin works, and then answer a few follow-up questions. These will be scheduled during the scheduled final exam time (Friday, 11 December 2-5pm) and other times.

18 Nov 2015

Schedule

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Litecoin boasts faster confirmations (2.5 minutes as opposed to 10 minutes). Does this help you gain confidence in a given transaction faster (at which point it is unlikely to be double-spent)?

16 Nov 2015

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Starting Wednesday and every following class: Be prepared to give an elevator pitch for your project. Your pitch should be no more than 2 minutes long. You may use visuals as long as you can obtain them by (quickly) entering a URL in a web browser. Your pitch should get across in a convincing and engaging way:

• 齐鲁晚报:2021-7-22 · 《齐鲁晚报》（电子版）的一切内容(包括但不限于文字、图片、PDF、图表、标志、标识、商标、版面设计、专栏目录与名称、内容分类标准众及为读者提供的任何信息)仅供齐鲁晚报的报、网、端、微等载体读者阅读、学习研究使用，未经本单位书面授权，任何单位及个人不得将《齐鲁晚报》（电子 ...
• What you are actually doing
• 西风vpn好用下载

Monday, 23 November (8:29pm): Project Progress Reports. Send an email to ccc-staff@cs.virginia.edu, cc-ing all members of your project team. The email should have a subject line, Project:Title, with your project title. Its body should contain at least this information:

1. A link to the website for your project (this could be a github page if you want). That site should have a front page that describes your project, lists the team members, and provides more information about your project.

2. A short paragraph explaining how your project has changed since the preliminary proposal email. This should explain if the goals of your project have changed and why.

3. A description of what progress you have made on your project.

4. 工信部回应“禁用VPN”：清理对象是无资质者_央广网:2021-7-25 · 工信部回应“禁用VPN”：清理对象是无资质者 在国务院新闻办今日举行的发布会上，有记者问及“有地方出台规定，对违法违规利用VPN上网加强管理”一事，工信部信息通信发展司司长闻库表示，不了 …

5. (optional) Any questions you have for us.

Addendum

武雪梅：苹果下架VPN是法治的胜利 - huanqiu.com:2 天前 · 日前，苹果公司CEO蒂姆·库克回应苹果应用商店中国区将VPN下架一事说，我伔在遵守当地法律的情况下在当地开展生意。一些网民将此事与去年苹果就是否协助执法人员“解锁”加州南部圣贝纳迪诺恐怖袭击案枪手之一所持的手机，与美国联邦机构对簿公堂、甚至要向总统陈情的事件对比展开热议。

The issue he noticed is that if the bank knows all the possible I values (all the customer identities), and receives one of the identity split perimages, e.g., I_1L, then the bank can search through all the identities to find an I_1R such that h(I_1R) matches the hash value. This is done by just xor-ing all the I values with I_1L to find a guess for I_1R, and then computing the hash to check if it is the right one. As I presented the scheme, this would be a big vulnerability! It violates the desired property that the bill spender’s anonymity is protected (even from the bank) unless she attempts to spend the bill twice.

To defeat this, we need to ensure that the set of possible I values is not known (even to the bank). One way to do this would be to add some randomness in the I values used in the generated banknotes used in the cut-and-choose for the blind signatures. Each note with have a different I, but one the bank can verify is still the right account owner. I’ll leave the details of how to do this as a challenge problem.

vpn被封翻墙党该何去何从？App Store连接不上如何解决？(图 ...:2021-1-29 · 前几天，据《环球时报》英文网报道中国已经开始屏蔽外国VPN服务，此消息也引起了国内“翻墙党”的一片震动。日前，工信部通信发展司司长闻库在接受采访时也被问到了这一问题，他回应称在中国发展互联网一定要按照中国的法律法规来进行，一些不良信息应该按照中国法律进行管理。

This page should contain everyone’s submitted project idea. We’ll keep this updated as the projects develop, so please let us know if things change (you can also post comments on the page for updates).

The slides from Alex and Nick’s presentation are now posted:
Scaling Bitcoin and Web Bitcoin Blockchain 2.0.

12 Nov 2015

Last class, we talked about using Graph Isomorphism as the basis for a zero knowledge proof, based on the assumption that it is a computationally hard problem to determine if two graphs are isomorphic.

Yesterday, Laszlo Babai presented a result that claims a quasipolynomial time algorithm for graph isomorphism (that is, shows graph isomorphism is not a hard enough problem to use as the basis for a zero knowledge proof).

Jeremy Kun’s summary of Babai’s presentation
A Big Result on Graph Isomorphism

Note that this has no bearing on the zero knowledge proofs based on the hardness of graph three-coloring, which, unlike graph isomorphism, is know to be NP-Complete.

12 Nov 2015

As Cyrus and Collin mentioned in class yesterday, Special Agent Jeremy D’Errico, who visited our class earlier in the semester, will be the guest speaker at the meeting of the 红豆博客:2 天前 · 伟人也讲“东风” “西风 ”。 得饶人处且饶人 物质丰盛时的节俭——《道德经》第五十九 .. 日排行 周排行 月排行 总排行 缘 彩臣乐乐 舞台因有节目而精彩 千叶花开 千叶花开的博客 ... tonight (Thursday) at 7:00pm. He’ll talk about Cryptowall malware and efforts to analyze and detect it.

The meeting will be in Thorton D223.

11 Nov 2015

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• Jean-Jacques Quisquater (Myriam, Muriel, Michael), Louis Guillou (Marie Annick, Gaid, Anna, Gwenole, Soazig), How to Explain Zero-Knowledge Protocols to Your Children. (Explains how zero-knowledge protocols work using a story about the Strange Cave of Ali Baba.)

• Ben Sasson et al. Zerocash: Decentralized anonymous payments from Bitcoin

• Miers, I.; Garman, C.; Green, M.; Rubin, A.D. Zerocoin: Anonymous distributed e-cash from bitcoin

9 Nov 2015

The slides from Nick Skelsey and Alex Kuck’s presentation about ombuds are here: Scaling Bitcoin and Web 西风vpn好用下载 Blockchain 2.0.

9 Nov 2015

Project Pre-Proposals are due Friday (November 13) at 8:29pm.

Your pre-proposal should include the following information:

1. 新民网 - 为民分忧 与民同乐:2 天前 · 新民网是新民晚报官方网站，强势新闻门户，众上海突发、财经、原创新闻为特色，采用文字、视频、播客、图片、直播等全媒体技术创新报道，另有当日新民晚报数字报纸和新民周刊数字杂志供应。

2. Title of your project - a short title that gets across what your project is about.

3. Idea for your project - one or two paragraphs that explain what the purpose of your project is and what you plan to do.

4. Expected outcome - what you hope will be the outcome of your project. This should explain what you expect to be able to deliver by the end of semester, and how the world will benefit from it.

5. Related work - list of projects (which could include papers, companies, etc.) that had goals related to yours. You do not have to have studied these in detail yet, but should have identified starting points to look at.

6. 齐鲁晚报:2021-7-22 · 《齐鲁晚报》（电子版）的一切内容(包括但不限于文字、图片、PDF、图表、标志、标识、商标、版面设计、专栏目录与名称、内容分类标准众及为读者提供的任何信息)仅供齐鲁晚报的报、网、端、微等载体读者阅读、学习研究使用，未经本单位书面授权，任何单位及个人不得将《齐鲁晚报》（电子 ...

Please submit this as a plain text email to ccc-staff@cs.virginia.edu.

Your email should have as its subject line: Project: Title where Title is the title of your project. It should include all team members as cc’d recipients. It should include your answers to the six points above, clearly numbered. Do not use any PDF attachments unless it is really necessary to provide a figure for your idea to be understandable.

4 Nov 2015

Schedule Updates

Monday’s class will be a visit from Nick Skelsey and Alex Kuck of Ombuds!

Problem Set 3 is due Sunday, 8 November (8:29pm).

Project Pre-Proposal: Friday, November 13

2 Nov 2015

Schedule Updates

Problem Set 3 is due Sunday, 8 November (8:29pm). Readings for PS3:

• Chapter 6: Bitcoin and Anonymity from Arvind Narayanan, Joseph Bonneau, Edward Felten, Andrew Miller, Steven Goldfeder.

• A Fistful of Bitcoins: Characterizing Payments among Men (sic) with No Names by Sarah Meiklejohn, Marjori Pomarole, Grant Jordan, Kirill Levchenko, Damon McCoy, Geoffrey M. Voelker, and Stefan Savage. Internet Measurement Conference, 2013.

Project Pre-Proposal: Friday, November 13

28 Oct 2015

Schedule Updates

西风vpn好用下载 is due Sunday, 8 November (8:29pm). Please don’t wait to get started so you have enough time to do something interesting and valuable for the open-ended questions.

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Project Pre-Proposal: Friday, November 13
Project Update: Monday, November 23
Last class: Monday, December 7

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Simeon-Denis Poisson, Recherches sur la probabilité des jugements en matière criminelle et en matière civile ; précédées des Règles générales du calcul des probabilités, 1837.

26 Oct 2015

Josh Cincinatti, Developer Advocate for BlockCypher (and UVa alum), gave a presentation on The Budding Business of Bitcoin and BlockCypher: An Alliterative, Allegorical Adventure into Cryptocurrency.

25 Oct 2015

Problem Set 3 is now posted, and is due Sunday, 8 November (8:29pm). You should have received an email with information on the bitcoin ransomware addresses to use for PS3.

23 Oct 2015

Monday’s class will be a guest talk from Josh Cincinnati. Josh is BlockCypher’s “Developer Advocate and Comedian”. He is a University of Virginia alum (Political & Social Thought and Mathematics) and has an MBA from Stanford. You can read several interesting posts of his on the 西风vpn好用下载.

For some background on the current entrepreneurial landscape in cryptocurrencies, Josh send along this report: The Blockchain Report: Welcome to the Internet of Value, Needham & Company, LLC, 21 October 2015.

21 Oct 2015

Class 16 was the Midterm Exam.

21 Oct 2015

The midterm exam is here: PDF

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Midterm Exam

The midterm exam will be in class, Wednesday, 21 October. The midterm will be closed-resources, but is meant to test understanding, not memorization.

The midterm covers: Classes 1-15, Checkups 1-2, Problem Sets 1-2, and the assigned readings: Chapters 1, 2, 3, and 5 from Bitcoin and Cryptocurrency Technologies; Chapters 1, 2, 3, 4, 6, and 7 from Mastering Bitcoin: Unlocking Digital Cryptocurrencies; Satoshi Nakamoto, 新民网 - 为民分忧 与民同乐:2 天前 · 新民网是新民晚报官方网站，强势新闻门户，众上海突发、财经、原创新闻为特色，采用文字、视频、播客、图片、直播等全媒体技术创新报道，另有当日新民晚报数字报纸和新民周刊数字杂志供应。; Ittay Eyal and Emin Gün Sirer, Majority is not Enough: Bitcoin Mining is Vulnerable.

The first two questions on the midterm will ask you to comment on the technical validity of some statements in the Congressional Research Service report (in the first 8 pages, not the policy issues).

Extra Office Hours. There will be some additional office hours this week:

• Monday, 5-6:30pm (Ori, Rice 442)
• Tuesday, 2-3:30pm (Dave, Rice 507) (Added)
• Tuesday, 3:30-4:30pm (Samee, Rice 442) (Added)
• Wednesday, 3:30-4:30pm (Samee, Rice 442)
• Thursday, 2:30-3:30 (Dave, Rice 507)

Scripting Transactions

Recall from class 12: Transaction outputs in bitcoin are protected by locking scripts, and must be unlocked by unlocking scripts. A transaction output is not unlocked unless an unlocking script is provided such that the result of executing the unlocking script, followed by executing the locking script, is a stack with value True on top.

15 Oct 2015

There will be some additional office hours next week:

• Monday, 5-6:30pm (Ori, Rice 442)
• Tuesday, 2-3:30pm (Dave, Rice 507) (Added)
• Tuesday, 3:30-4:30pm (Samee, Rice 442) (Added)
• Wednesday, 3:30-4:30pm (Samee, Rice 442)
• Thursday, 2:30-3:30 (Dave, Rice 507)

I hope these will be helpful in preparing for the midterm, as well as for discussing project ideas.

14 Oct 2015

Schedule

Today’s class was a visit from Special Agent Jeremy D’Errico, Special Benjamin Blome, David Cochran, and Stuart VonCanon from the Federal Bureau of Investigation (Richmond Division).

For Problem Set 3, you will be analyzing the blockchain to understand transactions involving bitcoin ransomware crimes. Some links to relevant posts and papers:

CryptoWall Ransomware, Dell SecureWorks Counter Threat, August 2014.

Tearing Down Cryptowall, Brian Wallace, 4 November 2014.

Amin Kharraz, William Robertson, Davide Balzarotti, Leyla Bilge, and Engin Kirda. Cutting the Gordian Knot: A Look Under the Hood of Ransomware Attacks. DIMVA 2015.

Shuang Hao, Kevin Borgolte, Nick Nikiforakis, Gianluca Stringhini, Manuel Egele, Michael Eubanks, Brian Krebs, Giovanni Vigna. Drops for Stuff: An Analysis of Reshipping Mule Scams. ACM Conference on Computer and Communications Security 2015.

12 Oct 2015

Schedule

Today’s class was a visit from Tom Dukes on law and policy related to cryptocurrencies.

Tom Duke’s Bio

The Congressional Research Service report he mentioned: Bitcoin: Questions, Answers, and Analysis of Legal Issues, 14 August 2015. This provides a good summary of US laws and regulations that apply to bitcoin, and why Congress is interested in it.

12 Oct 2015

一个神奇的网站:2021-3-23 · 本站文章部分内容转载自互联网，供读者交流和学习，如有涉及作者版权问题请及时与我伔联系，众便更正或删除。感谢所有提供信息材料的网站，并欢迎各类媒体与我伔进行文章共享合作。

In class on Monday, October 19, you will receive a handout that sets up and includes a few of the questions on the midterm (which you’ll be expected to work on before Wednesday, Oct 21, and will be able to bring in written answers to that you will submit as part of the midterm). The rest of the midterm will be in class on Wednesday, October 21.

If you have a problem with the schedule change and prefer to do the midterm on Monday, October 19, this is an option. You should contact Dave or Samee to arrange this by Oct 14 at the latest.

7 Oct 2015

Schedule

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Computing a bitcoin address: (bitcoinwiki)

1 Oct 2015

西风vpn好用下载 is now posted, and is due Friday, 9 October (8:29pm). Sorry it took so long to post this!

The other thing I hope everyone thinks about over “reading break”, is ideas for a course project. You can see projects from the course last Spring here: 工信部回应VPN指导意见:不会影响国内外用户正常使用 ...:2021-1-30 · 中国网1月30日讯国务院新闻办1月30日举行新闻发布会,华尔街日报记者就VPN相关情况在会上进行提问,"请您介绍一下于1月27日发布的关于VPN的指导意见 .... Your project can be anything related to cryptocurrencies or the tools we learn about in this class, and can be done individually or with a team (the size of the project should scale approximately with the square root of the team size). If you have an idea for an ambitious project that you want to start early, it may be possible to arrange for it to substitute for some other course assignments.

30 Sep 2015

Schedule

28 Sep 2015

If you didn’t get a “gold star” on Checkup 2, you can improve your score by answering one or more of the questions below. You can submit your revisions in class Wednesday, or at the end of office hours Wednesday. To submit revisions, attach your answers to these questions to your original submission.

R1. Hashing (Answer this question if you want to improve your score on questions 1-4)

There are several different places in bitcoin where cryptographic hashes are used:

A. Producing the public bitcoin address by hashing the public key.

B. Producing a transaction digest for use as the input in signing a transaction.

C. Producing the Merkle tree root for authenticating the transactions in a block (using hashes all the way up the tree).

D. Producing the hash of the previous block to use in the block header.

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Suppose H is a hash function that provides strong pre-image resistance, but does not provide collision resistance. That is, an adversary knows way to efficiently find pairs of values, m₁ and m₂ such that m₁ is not equal to m₂ and H(m₁) = H(m₂).

Explain clearly 西风vpn好用下载 where cryptographic hashing is used in bitcoin that the adversary could gain an advantage by knowing how to find collisions in H. (Be careful to not overstate the advantage, though.)

R2. Blockchain (Answer this question if you want to improve your score on questions 5-7)

Ishtosa suggests strengthening bitcoin by adding the hash of the previous previous block to the block header. So, the block header for block 534 would now include the both the hash of the block 533, and the hash of block 532. Would this be a good idea?

28 Sep 2015

Schedule

23 Sep 2015

The 西风vpn好用下载 starts with a story about bitcoin being used in a ransom scam (CryptoLocker). Its a sad story, without a lot of technical insights, but does give a sense of what the bitcoin experience is like for many people today. A good thing to think about for a potential project is how to solve the problem —- making it so bitcoin can’t be used to collect ransom untracably, without losing the desirable aspects of anonymity and decentralization.

苹果下架部分不符合规定的VPN应用程序_荔枝网新闻 ...:2021-7-30 · 据彭博社消息，苹果在中国应用商店下架部分不符合当地规定的VPN应用程序。”今天中国多家VPN提供商已收到了来自苹果公司的通知，通知主要告知了这些提供商和开发者，他伔的软件将从国区App Store中下架，因为这些软件包含了在中国不合法的 ...

21 Inc. Releases First Product, a ‘Bitcoin Computer’, Wall Street Journal, 21 September 2015.

23 Sep 2015

Schedule

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Checkup 2 (PDF)

As was suggested in class today, there won’t be an immediate opportunity to submit revisions for this (like there was for Checkup 1), but there will be some opportunity to improve your checkup result given in Monday’s class.

21 Sep 2015

西风vpn好用下载

西风vpn好用下载

You can subscribe to the course calendar. This has updated information on deadlines and office hours.

If you want to receive course website updates by email, you can subscribe to the RSS feed using a RSS reader or an emailing service like feedmyinbox.com or Blogtrottr. The feed address is http://bvhjyk.wcbzw.com/index.xml.

20 Sep 2015

Here are answers and discussions for the Checkup 1 questions. It would not be at all surprising if there are one or two questions on Checkup 2 (scheduled for Wednesday, Sept 23) that are closely related to questions on Checkup 1.

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16 Sep 2015

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Blockchain in the News

Blockchain initiative backed by 9 large investment banks, Financial Times, 15 Sept 2015.

Nine of the World’s Biggest Banks Form Blockchain Partnership, Re/Code, 15 Sept 2015.

Bitcoin Is Only The Beginning For Blockchain Technology, Forbes, 15 Sept 2015.

Bitcoin’s Shared Ledger Technology: Money’s New Operating System, Forbes, 9 Sept 2015.

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What are valid sources of trust?

14 Sep 2015

Schedule

9 Sep 2015

Schedule

7 Sep 2015

Checkup 1

Checkup 1 and Feedback.

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If you are not happy with your answers to any of the questions on Checkup 1, you may submit revised answers at the beginning of Wednesday’s class. (Just print the Checkup 1 and fill in revised answers for any questions you want, or submit your clearly marked answers on a separate page you generate. It is not necessary to resubmit answers to questions for which you are happy with your original answers.)

Schedule

2 Sep 2015

Schedule

2 Sep 2015

Here’s the up-to-date graph of hashing power distributed by mining pools (that I wasn’t able to find in class Monday):

http://blockchain.info/pools?timespan=4days

Looking at the current results for the past for days, more than 50% of the hashing power appears to be held by just three mining pools: F2Pool (20%), BitFury (17%), and AntPool (17%). Each of these has around 75 PH/s (one peta-hash means 10¹⁵ computations of the bitcoin block hashing function, which actually involves two computations of SHA-256).

We’ll talk about mining a lot more in the coming weeks to get a good understanding of what this means technically, as well as the implications for the blockchain.

2 Sep 2015

Problem Set 1 is now posted, and is due Tuesday, 15 September (8:29pm).

1 Sep 2015

The email address, ccc-staff@cs.virginia.edu, reaches all the course staff (Dave, Samee, and Ori). If you have a question that can be asked publicly, its best to post it as a comment on the website. But, for things that don’t belong as website comments, use that email address to reach all of us.

I’ve updated the course calendar to include all the deadlines, and encourage you to incorporate this into your calendar: use this link.

31 Aug 2015

Schedule

网站系统维护中，敬请期待！:2021-6-15 · 系统维护公告 尊敬的厦门网网友： 2021年5月20日21时至6月25日12时，海峡社区、海峡博客平台进行系统维护升级，系统将暂停访问，由此给您带来的不便敬请谅解。

Ori’s office hours have been moved to 5-6:30pm Monday (in Rice 442). All of our office hours are:

• Ori, Mondays 5-6:30pm in Rice 442
• Samee, 3:30-4:30pm in Rice 442
• Dave, 2:30-3:30pm in Rice 507

If you can’t make the scheduled office hours, send email to arrange another time.

26 Aug 2015

Schedule

26 Aug 2015

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First Class: Wednesday, 26 August 2015
Location: Olsson 120
Teachers: 西风vpn好用下载 and Samee Zahur

More information will be posted here soon. Until then, see the 西风vpn好用下载 and Last Semester’s Course.

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Blockchain initiative backed by 9 large investment banks, Financial Times, 15 Sept 2015.

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Bitcoin Is Only The Beginning For Blockchain Technology, Forbes, 15 Sept 2015.

Bitcoin’s Shared Ledger Technology: Money’s New Operating System, Forbes, 9 Sept 2015.

30 Aug 2015

There’s an article in the New Yorker, Inside the Fight Over Bitcoin’s Future, 25 August 2015 (by Maria Bustillos) about the split over the increasingly heated debate in the bitcoin community over the maximum size of a block.

The current maximum size accepted by the Bitcoin Core node software is 1MB (which means the network can support only approximately 7 transactions per second). There are lots of proposed solutions to this, including increasing the block size, but they are controversial and also raise lots of issues about how to make decisions like this for a decentralized system.

28 Aug 2015

New York Times, Bitcoin Technology Piques Interest on Wall St., 28 August 2015 (by Nathaniel Popper).

… the innovations that helped turn Bitcoin into the most popular virtual currency are now being viewed as a potentially enormous disruptive force for several industries, including accounting, music and journalism. Nowhere, though, are more money and resources being spent on the technology than on Wall Street — the very industry that Bitcoin was created to circumvent.

21 Aug 2015

There’s an article about the Ombuds project created by Alex Kuck and Nick Skelsey to use the bitcoin blockchain for communications:

Ombuds: Using Bitcoin to make online messages ‘immutable’, Journalism.co.uk, 20 August 2015.

Alex and Nick graduated from UVa in Spring 2015, and helped develop the 西风vpn好用下载, including creating the PointCoin cryptocurrency.